Outspoken WA MP says he'll stay with Libs

Maverick West Australian Liberal backbencher Rob Johnson says he won't leave the party despite concerns about its financial management and his dysfunctional relationship with the premier.

Mr Johnson has been one of Colin Barnett's fiercest critics since he was axed as police minister in a cabinet reshuffle in June 2012.

He prompted the second-term leader to walk out of the parliament chamber on Wednesday when he said the 2013/14 budget handed down last week showed the WA government had made election promises it couldn't afford.

On Thursday, Mr Johnson said it "meant nothing" to him that Mr Barnett didn't listen, but reiterated his party had made "policy on the run during the election campaign" and was set to rack up too much debt for its promised public transport projects.

"You don't take on debt that you're never going to be able to repay," he told Fairfax radio.

"I have to remind them ... and I want to get it on the record.

"We've got a lot of new members who, quite frankly, they don't necessarily understand the budget as it is, and they don't understand the ramifications of the debt."